PB2145: IMPACT OF A SIZE OF BONE PLASMACYTOMA ON THE COURSE OF MULTIPLE MYELOMA
Authors: Elizaveta Mamaeva, Maiia Soloveva, Maxim Solovev, Irina Kostina, Tatjana Obukhova, Larisa Mendeleeva
Journal: HemaSphere (2023)

Topic: 14. Myeloma and other monoclonal gammopathies - Clinical Background: Multiple myeloma (MM), complicated by bone plasmacytomas, is characterized by some features. The influence of bone plasmacytomas on the survival of MM patients is studied worldwide. A well-known factor of unfavorable prognosis in solitary bone plasmacytoma is the size: a large bone plasmacytoma has one of the linear dimensions exceeds 5 cm (D.Knobel et al.,2006). Learning of the impact of the size of bone plasmacytoma on the prognosis and course of the disease in patients with MM represents a considerable interest. Aims: to evaluate the impact of a size of bone plasmacytoma on the frequency of achieving a deep antitumoral response and survival in patients with MM. Methods: Retrospective single-center study from 2019 to 2022 included 58 patients (M:F-28:30) with MM aged 26 to 83 years (median 57 years), who were diagnosed with bone plasmacytomas at the onset of the disease according to low-dose whole body CT. All patients underwent routine laboratory tests, cytological examination of the bone marrow. Cytogenetic study by FISH was performed in 48 patients. Induction therapy included PAD or VCD in 40 patients, 17 patients received VRD, and 1 patient - DaraVMP. 30 patients underwent auto-HSCT. Statistical analysis was performed using the χ2 test for qualitative variables. Overall survival (OS) and progression-free survival (PFS) curves were built using the Kaplan-Meier method. Results: According to the results of low-dose whole body CT large bone plasmacytomas (>5 cm) detected in 39 of 58 patients: 1 large bone plasmacytoma detected in 28 patients, 2 or larger bone plasmacytomas detected in 11 patients. It was noted that the presence of 2 or more large bone plasmacytomas is a sign of an aggressive course of MM. Among these patients, ISS stage III diagnosed 3 times more often (67% versus 25%). High cytogenetic risk confirmed in all patients with few large plasmacytomas, while among patients with 1 large plasmacytoma it was only in 25%, and in the group of patients with small bone plasmacytomas, all were diagnosed with cytogenetic aberrations from the standard risk group (p=0.004). Among transplant-eligible patients with large bone plasmacytomas, there was a trend towards a low frequency of achieving a deep antitumoral response (VGPR and deeper) both after induction therapy (13.5% versus 37.5%, p=0.167) and after auto-HSCT (45.0% versus 83.3%, p=0.086). Among non-candidates for auto-HSCT, the frequency of achieving a deep antitumoral response was also lower in the presence of large bone plasmacytomas: 23.5% versus 42.9%, p=0.353. There is a trend towards a decrease in PFS and OS parameters in the group of transplant-eligible patients with large bone plasmacytomas: 3-year PFS was 49% versus 100% in the group without large bone plasmacytomas (p=0.074), 3-year OS-80.2% versus 100% in the group of patients without large bone plasmacytomas (p=0.339). It turned out that the worst survival rates were registered in patients with 2 or more large bone plasmacytomas: median PFS 13.1 months (Fig.1), median OS 18.1 months. At the same time, in the group without large bone plasmacytomas and with 1 large bone plasmacytoma, the median PFS and OS weren’t reached. Among non-transplant eligible patients, there were no significant differences in PFS and OS between the compared groups. Summary/Conclusion: Presence of a large bone plasmacytoma negatively affected frequency of deep antitumoral response achievement and survival of patients with MM. Most prognostically unfavorable was a group of patients with 2 and more large bone plasmacytomas. Figure 1. Progression-free survival of patients with multiple myeloma depending on the number of large bone plasmacytomasKeywords: Survival, Autologous hematopoietic stem cell transplantation, Multiple myeloma